1. The Field of the Invention
The present invention relates to the field of dentistry, more particularly to endodontic cones, such as those made of gutta percha, used in filling root canal chambers.
2. The Relevant Technology
When a dental practitioner performs a root canal, pulp and other material in the root canal chamber is removed. Once a dentist has removed diseased and soft tissue from a tooth's root canal, the chamber must be filled. The purpose of filling the root canal is to seal the area, and to eliminate the possibility of bacterial attraction and infection in the chamber. Filling and sealing the chamber is necessary to prohibit material from draining into the canal, which could attract bacterial contamination of the root canal chamber. In addition, filling the chamber provides a base that may be drilled out later for placement of one or more posts to which may be mounted a crown or other restorative appliance.
The current method of filling the root canal is by inserting shaped cones of gutta percha into the prepared root canal. Gutta percha typically includes a matrix of trans-isoprene, zinc oxide filler, a radiopacifier such as bismuth, barium or strontium, wax or resin, color pigment, plasticizers and other additives. One difficulty with using gutta percha has been that it does not readily bond to and seal against the tooth tissue. Tooth tissue is quite hydrophilic, while gutta percha itself is extremely hydrophobic. Typical endodontic pastes, used to bond and seal the gutta percha to the tooth tissue, comprise zinc oxide and eugenol. This mixture is also hydrophobic, and while it bonds quite well to the gutta percha, its bond with hydrophilic tooth tissue is often poor. In addition, eugenol is believed to act as a polymerization inhibitor, which can also result in poor bonding and sealing in the event polymericable resins are used.
Recently, hydrophilic resins have been developed which bond much better to tooth tissue, but they may still bond poorly to gutta percha because of its extremely hydrophobic nature. The result may be a root canal chamber that is not completely sealed, which increases the chance of irritation of the affected area or bacterial contamination, leading to infection and possible failure of the root canal. The level of discomfort and pain associated with an irritated, inflamed, and/or infected root canal area can be great, followed by loss of the tooth.
As one solution to this problem, U.S. Pat. No. 6,986,662 proposes providing an endodontic cone to which a particular adhesive coating has been attached during manufacture so as to render the cone more chemically compatible with a hydrophilic sealing resin. The adhesive includes a hydrophobic portion that is chemically compatible with the gutta percha substrate and a hydrophilic portion that is chemically compatible with a hydrophilic resin. The adhesive may be applied by dipping or brushing during manufacture. While such a manufactured endodontic cone appears to solve the problem of poor bonding between the tooth tissue, the sealing resin, and the gutta percha, the present inventors have found the manufacturing process including coating of the adhesive to be extremely messy and difficult to perform. For example, the adhesive can easily clog and gum up manufacturing equipment, requiring frequent shut downs, cleaning, and maintenance, which makes it difficult and relatively expensive to produce coated endodontic cones on a mass economic scale.
It would be an improvement in the art to provide kits and methods that would solve the poor bonding issues, while also minimizing or eliminating the difficulties and messiness associated with current manufacturing methods.